Variable pitch propeller



Oct. l0, 1961 F. E. CONN ET A1 3,003,566

VARIABLE PITCH PROPELLER Filed oct. 1o, 1958 11 sheets-sheet 1 N Q 6mm/faam N Q FokcE N THEIR ATTORNEY Oct. 10, 1961 F. E. CONN ET AL 3,003,566

VARIABLE FITCH PROPELLER Filed 06f.. 10, 1958 l1 Sheets-Sheet 2 Q =lu u l@ Q a 506 605 55e LA fnv/acs THE/R ATTR/Viy Oct. 10, 1961 F. E. CONN ET AL VARIABLE PITCH PROPELLER 1l Sheets-Sheet 3 Filed Oct. 10, 1958 Oct. 10, 1961 F. E. CONN ET Al. 3,003,566

VARIABLE FITCH PROPELLER .40 l l fw THe/R ,erro Nfy Oct. 10, 1961 F. E. CONN ET AL 3,003,566

VARIABLE FITCH PROPELLER Filed Oct. 10, 1958 11 Sheets-Sheet 5 ,m RS

/NMENToRS Fmfzczs E. Comi Call/m C. Covey? Hinz( A. /IZof/ce dz/[zam A. lezs THE/R ATTORNEY Oct. 10, 1961 F. E. coNN ET AL 3,003,566

VARIABLE PITCH PROPELLER Filed Oct. l0, 1958 l1 Sheets-Sheet 6 4,/ /y gif/ rfa 4141i fn? THEIR 70K/V57 Oct. 10, 1961 F. E. CONN ETAL VARIABLE FITCH PROPELLER l1 Sheets-Sheet 7 Filed 001'.. l0, 1958 THE IR ATTORNEY UCL 10, 1961 F. E. coNN ET AL 3,003,566

VARIABLE FITCH PROPELLER Filed oct. 1o. `195sA 11 sheets-sheet e s 'Il' big Il uw l l/ A lll/lll///// /NvE/vTo/es Fra/vds j Camz :b Cali/121 C. Coz/e127* Elim; lf. Z/Yazv'e @n Ldlzam A. de/s .N BY

3 l (t f 7745112 AT amv/5y Oct. 10, 1961 F. E. CONN lrAl.y 3,003,566

VARIABLE FITCH PROPELLER Filed oct. 1o, 195s 11 sheets-sheet 9 THE/R ATToR/VEY Oct. 10, 1961 F. E. coNN ETAL 3,003,566

lVRIABLE PITCH PROPELLER Filed Oct. 10, 1958 11 Sheets-Sheet 10 THE/K TTORNE Y Oct. 10, 1961 F. E. coNN ErAL 3,003,566

VARIABLE PITCl-I PROPELLER 11 Sheets-Sheet 11 Filed Oct. 10, 1958 /N VENTO/Q5 .Ffazczs E. Camz 2W on, ar/c BY d/Imm .4. dels THE/R Afrox/ver United Se@ Patent@ 3,003,566 VARIABLE PITCH PRGPELLER Francis E. Conn, Piqua, and'Calvin C. Covert, Elton K. Morice, and William A. Weis, Dayton, Ohio, assignors to General vMotors Corporation, Detroit, Mich., a corporation o f Delaware Y Filed Oct. 10, 1958, Ser. No. 766,611 20 Claims. (Cl. 17d-160.21)

tageous to incorporatepilot,operated means for adjusting the speed setting of the governor to match the power,

output of the turbine throughout the forward thrust range. Moreover, in order to obtain maximum reversing thrust it is advantageous to incorporate a reverse governor whereby propeller speedis maintained substantially constant at full rated speedvto absorb full turbine power during landing. The present invention relates to a variable pitch propeller including pilot controlled speed scheduling means operable in the forward thrust rangeyconstant speed governing means ,operable iny the reverse thrust range; hydraulic stop means for establishing minimum positive and minimum negative blade. angles in the forward and reverse thrust ranges, respectively; and mechanically operated self-seeking feathering mechanism.

Accordingly, among our objects are the provision of a hydraulically controlled variable pitch propeller including governing means operable to maintain propeller speed substantially constant in the forward and reverse thrust ranges; the further provision of a forward and reverse thrust governor including means for adjusting the speed setting thereof during operationl in the forward thrust range; the further provision of means for changing the operating characteristics of a speed sensitive governor system between forward and reverse thrust; the further provision of adjustable hydraulic low pitch stop means for establishing minimum blade angles during governing in the forward and reverse thrust ranges; and the still further provision of lmechanically operable means for automatically moving the propeller blades of a hydraulically controlled variable pitch propeller to an optimum feather blade angle if the propeller rotates after the blades are moved into the feathering range.

The aforementioned and other objects are accomplished in the present invention by providing a self-contained hydraulically operated propeller with externally adjustable mechanical controls. Specifically, the propeller assembly includes a hub having a plurality of blades journalled therein for movement about their longitudinal axes between a maximum negative blade angle'position and a fully feathered position. Each propeller blade is rotated by an independent torque unit disposed within the hollow shank portion thereof, which torque units may be of the type shown in U.S. Patent 2,734,587. The blade angle positions of the several propeller blades are coordinated by a master gear assembly rotatably journalled in the hub and drivingly connected with the blade gears of all the propeller blades. Y

The master gear assembly hasV a denite angular position with respect to the hub for each blade angle position of the propeller blades, and accordingly, releasable mechanical pitch lock means and releasable mechanical low pitch stop means are incorporated in the propeller hub" The mechanical pitch lock and low pitch stop assemblies may be of the type disclosed in copending application Serial L No. 571,523 tiled March 14, 1956, in the name of Hirsch'4v et al. and assigned to the assignee of this invention, now y and operatively associated with the master gear.

Patent No. 2,882,975.

The propeller hub is journalled for rotation abouta stationary support shaft. The propeller hub is drivingly connected to the output shaft of the turbine through a hollow drive shaft coaxially disposed within the stationary support shaft and drivingly connected to the forward portion of the hub. ln order to achieve full feathering, the master gear assembly is coupled to the stationary support shaft'through a feather seeker clutch when the propeller blades are moved into the feathering range by hyf' Accordingly, if the pro-, peller should rotate after the blades have been hydraulidraulic fluid under pressure.

cally moved into the feathered range the blades will be mechanically moved to a fully feathered position wherein the propeller hub does not rotate relative to the stationary support shaft.

An air cooled reservoir for hydraulic uid is attached Y to the forward portion of the propeller hub, and an electric motor driven feathering pump and a mechanically driven feathering pump are disposed within the reservoir. continuously during propeller rotation, but the output thereof is normally by-passed back to the reservoir so that the mechanically driven feathering pump is normally unloaded. The electric motor driven feathering pump can be energized by the pilot at any time to feather the propeller blades.

ulator.

valve assembly, a feathering valve assembly, a pitch lock and pitch stop control valve assembly, a reverse governor selector and a solenoid valve assembly. Some of these valve assemblies are capable of external control through a plurality of nonrotatable axially movable control rings disposed within the regulator and supported by a stationary adapter assembly. In the instant propeller, three control rings are utilized, namely, a synchronizer control ring, a propeller control ring and a negative torque signal control ring.

The propeller control ring is controlled by the pilot through the propeller control lever whereby the pilot can select operation in reverse thrust governing, manually selected blade angles in the beta range, forward thrust governing and emergency feathering. The propeller control lever is movable between a full reverse position through a reverse governing range, through a blade angle selecting range, a forward thrust governing range toa In the forward thrust governfull feathering position. ing range, the pilot can manually adjust the speed set ting of the governor between predetermined limits up to the full rated speed setting. When the propeller control lever-is in the blade angle selecting range, the pilot can manually select any angle between a minimum positive blade angle of the forward thrust governing range and a `l minimum negative blade angle in the reverse thrust governing range. When reverse governing is selected the propeller control lever must be moved throughout the beta range so that the propeller blades will be moved to a minimum negative blade angle setting when the sense of the governor is reversed.

. Patntedocuio, 1961 The mechanical feathering pump is driven encargan The synchronizing control lever for adiusting the position of the synchrniz'er control ring in the regulator may be actuated by an electromechanical lsynchronizer f the type Shown in. @pending application.V Serial. Ne 630,234 tired December 2,1; 1956,*iarhenameqf Broeken, et. allv and 'sienedto the. assignee'. Qi. this-illumina. The. negative torque signal control -lever may be mechanically connected Atofany suitablevnegative torque sensing deviceV infthewgear box of the turbine so asto actnate the. feather?. ingvalve inthe regulator andthereby. cause. udjllldl' pressure to be supplied to the torquey units to increaae propeller pitch towards the. featheredposition,

`-lr'ther objectsand advantages ofthe presentinventionw willA be apparent from thefollowng descriptiomreference. beinghad to the accompanyingdrawings, whereinahprea ferred embodiment, of the present` invention is clearlyV sh'siwn- In the drawings:

EIGURES 1A, 1B and` 1C constitute a schema-ticfdia. gram showingthe'propeller and its control.mechanism.y

NFIGUREZ/is a schematic diagram'depicting operation ofthe governor in the reverse thrust range. w

`FIGURE 3 is a fragmentary view,y partly in section and partly in elevatign @fa propeller-Coneruted.awarding-i0 the'present invention.

FIGURES 3A and 3B are enlarged fragmentary views,y partly in section and partlyin elevation, ltalgen:a'longlines SATSA and 3B-:3Bof FIGURE 4.

EIGURE 4 isa fragmentary. View, partly inrsection andv partly in elevation, taken along, lines. 4.-,4' o-f EIGURES--, BAvand 3B.. I

IIQURE 5 iS annlareed. View, partly inectonand. partly in elevation, takenalong lines S-SotEIGURE: 4.

ylIUliE 6 is an. enlarged ,fragmentary vView,.partly SeFIIOn andA partly :flteleviiala ,tekenalfieliies, 6.-:61Qf.. FIGURE 4.

FIGURE 7 is a fragmentary View withcertainparte;4 broken away, taken along linaje-.7 OLEIGURES;

EIGURE. 8 is a viewsi r. to EIGURBgvvitlahite;I parts'adjusted 'for operation` u* reverse .governingi and With particular referencetoEIGURES1A, lljandilQ, whereinthe propeller andv the controlsystem thereforare depiffeY schematically, the: propellninclndes;ahnb 1.9, having a plurality ofradially extending socketslZmwithing which Apropeller bl`ades1g4. are` journalled by stack bearings 11i-tor rotation about their;longitudinalV a xesbetween; a; maximum negativeblade angle, foreiramplev 133y and fully feathered b lade. angle. Eachtpropelleryblade.has af hollow shanlr` portion within which iluid motor meansiforr:v rotating the propeller.vr blade about itsA longitudinalaxis are disposed, these motor means comprising `a cylinder` 1 3l having a reciprocable piston 20 disposedthercin, The .in. ner wall of the cylinderv 15 is helically-splined as indicated by..numeral 22- andthe piston isnformed- Yw-ith externall helical spline teeth 24 whichrnate with-thespline teeth 22. In addition, the piston 20 isfformed with internat helical spline. teeth 26 which mate with external helical spline. teeth 28 formed on a xed reactionmember 30.- Accord,-V ingly, reciprocationof -thepistonZi) will be accompanied by angular` movement thereof,v which angular movement is imparted tothe propeller blade 14 seas to-vary the pitch: positionithereof.A` ThepisrtonwZtG divides the cylinderH 18 into a. decrease pitch chamber-3 2 and vanincrease'pitch chamberv 34, which communicate-respectively with con. duits 36 and 3S. Theymagiimum negativeangle ofthe propeller `bladespisdetermined by engagement between the pistonvZtl and the lower end wall of the cylinder as depicted in FIGURE: 1C,lwhere as the maximum positive angle isv determined by engagement of the piston 20.with the top of the` cylinder 18.

Each blade 14 is connected-to a bevel gear sector. 49, and the several sector blade gears mesh with abeveltype master gear 42 which is iournalled Ain the Ahub -10 `for rotation about the horizontal` propeller axis indicated by numeral 44 in FIGURE 1C. The master gear 42 has a definite angular position relative to the propeller hub 10 for each pitch position of the propeller blades throughout their range of adjustment:4 The; master gear 42 has an integral axally.- extending; Skim 45' having ratchet teeth tffnrimed Qnfheend airfarethereof.4 The-ratchet teeth' 46 cangbe.engagedbvacomplementaryfset of ratchet teeth 4S formed` on anannulusfSO,4 and when the ratchet'teeth 48 engage thgeratchet teeth 4,6,rotation ofthe master gear 42 is precludedlingone directiomto prevent movement of the propeller blades 14 in the decrease pitch direction, Whiltevpermitting rotationy of, the propeller blades about their longitudinal axes intheiperease pitch direction. The annulus` 50v andthe sllirtAS., o f the master gear 42 con- Stute a mehanicalppitchlocl. 'lhe-.annulusSO is formed witha piston surfacefSZ andjsgmovable axially out of engagement withI the master1 gear 42. upon the application of uid under pressure tQa servo chamber 54. The annulus 50,v haa; a` straight splineconnectionl 56 with the, hub 16 whereby rotationnf theannnlusrelatire to the heb. iS nrw eluded... Whereasr relative-` a .iiial movementv therebetween is remitted.

Themaster ee.a.r.;42.isdepicted.schematically as being inteeralwth..asieevewhchis;shown schematically es being' integral. with. an. annulus.. 60. having; a. partially toothed` periphery 6 2 andal plurality ofjycircumferentially.. Specdaxially extending iawi- The. jaws 6.4 are engageable with jaws 6 6 formedon an annulins 68,. The anrullu's` 68;.hjas1a s traightspline connection a t70 withthe Runnin-$-50. audience yislrfeet'r.filmed. .against rotation. relative i0.th.e.hn.b 1.0. Whilelfreetomayeavielly relative thereto The... jaws.. 6.4. and.` 61.6,. cnnetitilte` aI mechanical low pitch Step, andthevannulns .canbemoi'ednut'Ofensaaement withthe annulus' GQ by. theapplicatonofuid under pres- 5112.619. @Sen/0.. Chamber. 7.2. Rreseureinlhe Senn Cheer bery 72 /actsvonmappistonsurfacejt. formed as an integral Partof theannulus' Theaxally movable-pitch StOp air nulas. @and thermally moveblepitch lock -anniilus Se are movable into engaging positionsby commonresilient means-.76 in. .dietarmfofa plurality otcfiilspriiesi Opposite endswhihngage the Backideeof piston @effacs and 74, re spectivelyl- Thesprings areperative to move thepitch lock annplustiinto anengaging" position in the absence ofthe application of,pressure fluid to the servo chamber 5,4,.and` thetspringsfm'. are liigewiseoperative to move thepitchgstop anulus'68 into anengaging position inpthevabsenceofLuid-preesurein the servo chamber 77;.

As: willLbe pointedotmore particularly hereinafter, thehub 10 is journalled for rotation about a fixed support Shaft.indicatedshemiatally inFIGURE 1C.. by numeral 78j. Avring` gear; 891s rigidly connected to thexed support shafpt,78. the ,ring geary 30; being formerly/ith a sei'- rated endsurrfaceeSZ, An annularclutchmernber 34 isV formeduwithV acomplementaryserrated end surface 86, thev clutch member Sfzhaving astraightspline connection at 88 with the sleeve 58. In, addition, the clutch nien ber t3 4.hasa plurality. of:eircurnferentially'v spaced axially extending. lugs 9 0..whficl1 areengageable wi-thr. complementary. set ofvcircumferentialiy spaced lugs 3 2 formed on the hub 1 0. Ille-.clutch member S4 isturged toward thering gear Stvby a-Bellevillespring 94 disposed betweentheclutehmember'Sanddthe annuius'). The coasting lugs 9 0 andSlZ4 prevent. axial movement ot"V the clutch member 84. into engagement with the ring gear Se at all times when,theprope-llerbladesarevat an angle less 'than avpredetermined highy positiveangle of for instance 86; The .feathering range. ofvthegpropeller may be considered as being.;betweenapoaitive 'and' affully feathered posi.- tio n When the bladesare-:moyed-to-thefeathering range, the,y lugs 90and9 2 arefdisengaged-whreupon-the Belleville spring 94 can move the clutch' member 84 into engagementlwith the ring `gear 80.V Under these conditions, the clutchmemberi'84; the/sleevel 58= and hence-the master gear 42 arerestrained against# rotation relative to the stationary support shaft`78. Consequently, rotation of the propeller hub 1h about the stationary support shaft in either direction will cause relative rotation between the master gear 42 and the blade gears 40' so as to mechanically drive the propeller blades to the fully feathered position, and when the propeller blades are in the fully feathered position the propeller will not windmill and hence no rotation will be imparted to the hub 10. Forward propeller rotation will result in increasing the pitch position of the blades whereas reverse propeller rotation will result in decreasing the pitch position of the blades.

The partially toothed periphery 62 or the annulus 6) constitutes an intermittent feedback drive gear. Structurally, the intermittent feed-back assembly may be of the type shown in Hirsch IPatent No. 2,761,519, and the partially toothed periphery 62 meshes with a pinion gear 96 attached to a rotary feed-back shaft 93. 1n the instant propeller, rotation is only imparted to the feedback shaft 9S during movement of the propeller blades from a 15 to a +l8. At all other times, the pinion gear 9o and the shaft 98 are restrained against rotation relative to the hub 111. The feed-back shaft 98 is formed with a high lead screw portion 1111i which engages a nut 162 shown schematically as being integral with a rod 11%4.

A feathering reservoir 166 is attached to the front of the hub 10, the feathering reservoir being maintained full of oil at all times. An electric motor operated feathering pump 1118 is disposed Within the reservoir 106, the delivery side of the pump 1118 being connected to a conduit 116. In addition, a mechanically driven feathering pump 112 is disposed Within the reservoir 1616, this pump being driven by a pinion gear 1111 through a shaft 116. The pinion gear 114 meshes with the ring gear 80, and hence whenever the hub rotates relative to stationary support shaft 73, the pump 112 will be operated. The output side of the pump 112 is connected to a conduit 11.5. The reservoir 106 is air cooled as will oe pointed out more particularly hereinafter, and ismaintained full of oil since a certain amount of the drain oil from the regulator is directed to the reservoir 1115 through a conduit 12d. A predetermined minimum pressure is maintained within the reservoir 106, since the oil flowing through the drain conduit 12d must open a spring biased check valve 122. before it can ilow into the reservoir 1116. The check valve 122 may be set to open at ya minimum pressure of 20 psi. In order to circulate oil from the regulator to the reservoir and bach to the regulator, a pick-up tube 12d having an inlet at the center of the reservoir 1% is provided. The tube 124 connects with the regulator reservoirthrough a spring biased check valve 12d. lSince the reservoir 1Go rotates with the propeller 1t), it will be appreciated that the oil in the reservoir will be thrown outwardly by cen Lifugal -torce and hence it is only when the reservoir 10u is full of oil that the overiiow will return to the regulator through the tube 124.

With particular reference to FIGURES 1A and 1B, the components of the regulator assembly are schematically depicted. The fluid pressure system includes three pumps 12S, 1311 and 132 which are driven incident to propeller rotation. The pumps 128 and 13@ draw iiuid from the regulator reservoir and discharge it through check valves 134 and 13o, respectively, to a conduit 13d. The conduit 138 is connected to a conduit 14d constituting a high pressure supply conduit. The pump 1.32 is connected to an auxiliary pump control valve assembly 142 through a conduit 144i. The auxiliary pump control valve assembly 142 includes a spring biased check valve 146, the outlet side of which is connected by conduit 148 to the conduit 138, an equal area type pressure control valve 1511 and a ow control valve 1512. The pressure cont-rol valve 151) includes a land d for controlling a drain port 156 which is connected to a conduit 158. When the pumps 123 and 136 can supply the iiow and pressure requirements of the propeller control system, the pump 1.32 is unloaded and the output thereof is by-passed into the drain conduit 153. The flow control valve152 includes a' sage 167 controlled by a second land 168 on the flow con-l trol valve 152. However, in the absence of fluid under pressure in conduit 162, the spring 164 and the thrust of centrifugal force will move the valve 152 upwardly so as to connect the passage 1617 with a conduit 171i. As will be pointed out more particularly hereinafter, the conduit 17, is subjected to the higher of the pressure dierentials existent in the increase and decrease pitch chambers of the torque unit, and when this pressure acts ou the lower surface or" the land 154, the pump 132 will be loaded whereupon the output of the pump 132 will be connected through the check vaive 146 and the conduit 14S through the conduit 13d. ihus, when the pumps 128 and 1311 cannot supply the flow requirements of the control system, the pump 132 will be connected into the system.

The high pressure supply conduit connects with a branch conduit 172 as shown in FIGURE 1B, a spring biased check valve 174 and a passage 176 in a feathering valve assembly 178. The propeller control system also includes la solenoid valve assembly depicted generally by the numeral 13h, a pitch lock and pitch stop control valve assembly 132, a governor valve assembly depicted by the numeral 13d, and a reverse governor actuator depicted by the numeral 18d. The feathering valve assembly 178 includes a servo actuated shuttle valve 18S having spaced lands 1911, 192, 194i, 1% and 198. The shuttle valve 138 is normally maintained in the position shown by a spring 2%. Passage 176 connects with a port 202 of the shuttle valve bore, the shuttle valve bore also including ports 204i, 266, 293, 211B, 212, 214, 216 and 218.

are interconnected, the ports 206 and 212 are interconnected, and the ports 216 and 218 are interconnected. Port 2M connects with a passage 22h having a spring biased check valve 222 therein which opens at a predetermined minimum pressure and connects passage 220 to conduit 223. The port 214 is connected byan internal passage to a port 224 of a solenoid operated valve 226. The valve 226 is maintained in the position shown in FIGURE 1B by a spring 22S when the solenoid 230 is deenergized. Upon energization of the solenoid 230, the valve 22o` moves to the right so as to interconnect ports 224 and 232 whereupon uid under pressure will be supplied from the conduit 14d through passage 176, ports 2%2 and 21d through ports 224 and 232 to the port 219 so as to move the shuttle valve downwardly. When the valve 226 is in the position shown in FIGURE 1B, the port 232 is connected to drain through a passage 234.

The feathering valve assembly 178 also includes a selector valve 23o. When the selector valve 236 is in the position shown in FIGURE 1B, the passage 234 is connected to drain. However, upon downward movement of the selector valve 236 the passage 234 is connected to a passage 23S, the passage 238 being connected to the pressure supply passage 176, whereupon port 210 of the shuttle valve will be connected to the pressure supply conduit 1.4i) through passages 176 and 233, passage 234,

and port 232 so as to move the shuttle valve 188 down- Wardly.

The feathering valve assembly 178 also includes a decrease loader valve 240 comprising a spring biased check valve which is operable to interconnect passages 242 and 24o when the pressure potential in passage 242 exceeds the pressure potential in passage 246 and the force of the spring 248. The passage 246 is connected through ports fi 266 and 212 when the shuttle valve 188 is in the position shown in FIGURE 1B to the decrease pitch conduit 36.

The delivery conduit 11G of the electric motor driven feathering pump lid-S connects with a port 250 of a feathering pump control valve 252. The feathering pump control valve 252 includes a housing having a `reciprocable sleeve 25d disposed therein, the sleeve 254 having sets of ports 256 and 25S. The sleeve 254 is urged upwardly as viewed in FIGURE 1B by the thrust of centrifugal force in the direction of arrow 166, and upward movement of the sleeve 254 is opposed by a spring 260. A reciprocable plunger 262 is disposed within the sleeve 254 and urged upwardly by a spring 26d, the spring 26) being stronger than the spring 264. The plunger 262 controls the connection of ports 25S with the drain conduit 12d. The valve assembly 252 operates to control the output pressure of the electric motor driven feathering pump 108 such that if the feathering pump is energized during propeller rotation, the port 256 will be blocked by the sleeve 254 so that the full output pressure of the pump 108 will be delivered through check valve 174 to the high pressure supply conduit 149. However, as the speed of the propeller rotation decreases, the spring 266 will overcome the thrust of centrifugal force and move the sleeve 251i downwardly as viewed in FIGURE 1B whereupon the port 25) will be connected with port 256 so that the plunger 262 will be subjected to the output pressure of the feathering pump. if the output pressure of the feathering pump exceeds the opposing force of the spring 264, the plunger 262 will move downwardly and connect ports 258 to the drain conduit 12) and thereby relieve the system pressure. In the instant propeller, the valve assembly 252 will operate to relieve the system pressure when the propeller rotation is below 600 r.p.m. when the output pressure of the feathering pump exceeds 45) p.s.i. The maximum delivery pressure of the electric motor driven :feathering pump may be on the order of 4500 p.s.i.

The solenoid valve assembly i8() includes a valve housing having a reciprocable plunger 266 therein which is normally centered by a pair of springs 268 and 27). The plunger 266 includes armatures 272 and 274 encircled by solenoid coils 276 and 278, respectively, such that upon energization of the solenoid coil 276 the plunger 266 will move to the right, and upon encrgization of the solenoid coil 278 the plunger 266 lwill move to the left. The solenoid valve housing includes a pressure supply port 2S@ and a pair of control ports 282 and 28d. The port 284 is controlled by a land 253 and the port 222 is controlled by a land 289, the land 289 being appreciably wider than the land 288 such that the port 282 is never connected to the pressure supply port 230. The port 2&2 connects with a conduit 294i, the con-duit 236 being connected to the decrease pitch conduit 36. The port 234 connects with a conduit 292 through a pressure compensating valve assembly 294. The pressure compensating valve assembly 294 includes a one-way spring biased check valve 296 and a pressure reducing valve 298. When the port 280 is connected to the port 234, uid under pressure is supplied to the conduit 292 through the check valve 296. The conduit 292 is connected with the increase pitch conduit SS through ports 21S and 216 of the shuttle valve 158 when the shuttle valve is in the position depicted in FIGURE 1B. When port 284 is connecte to the pressure supply 280, the port 282 is connected to drain. However, when the port 2% is connected to drain due to movement of the plunger 266 to the right, the port 232 remains blocked by the land 239. Under these conditions, the conduit 292 can only be connected to drain through the pressure reducing valve 29S, and the pressure reducing valve 298 operates to maintain a constant pressure in chamber 306 so as to control the rate of drain flow from the increase pitch chambers and thus control the decrease pitch change rate of the propeller.

The pitch lock and pitch stop control valve assembly 182 includes a servo actuated pitch lock control valve 302,

servo actuated pitch stop control valve 304, a mechanically actuated valve 306 for controlling the servo valve 364, a speed sensitive valve 368 for controlling the servo valve 362 and a flow sensitive valve 310 for controlling the servo valve 362. Substantially constant low pressure oil is supplied to the pitch lock and pitch stop control valve assembly 182 through conduit 312. When the servo operated pitch lock control valve 35i?, is in the position shown in lFIGURE 1B, reduced pressure is supplied through passage 314, passage 314 communicating with the servo release chamber 54 of the pitch lock. The reduced pressure also connects with a port 316 of the speed sensitive valve 368, the port 316 being connected at all times to a port 318 of the yliow sensitive valve 310. When the flow sensitive valve 310 is in the position of FIGURE 1B, port 313 is connected with the port 320 so as to supply reduced pressure to port 322 of a sleeve 324 constituting a valve guide for the speed sensitive valve 368. When the speed of propeller rotation in the forward thrust governing range does not exceed the speed setting of the governor by more than rive percent, the speed sensitive posing force of spring 326 is controlled by the position1 of bellcraclt nos, one end of which is connected to a seat for the spring 336 and the other end of which is connected to an adjustable rod assembly 346.

The flow sensitive valve 310 includes a land 342 which is subjected to pressure from a conduit 158-. Accordingly, when the pomp 132 is not connected into the system, the flow sensitive valve element will be maintained in the position shown in FIGURE 1B against the opposing force of a spring 3144. in the absence of drain flow in the conduit 158, indicating a loss of liuid pressure in the propeller control system, the spring 344 will move the valve 320 upwardly thereby connecting port 329 to drain whereupon the spring 332 will move the pitch lock control valve 302 upwardly and conneet passage 314 to drain enabling the spring '76 to move the pitch lock annulus 59 into engagement with the master gear 42.

The mechanical pitch stop annulus '74 is normally maintained in a position where it can engage the lugs on the -annulus d when the propeller is operated in the forward thrust governing range and the propeller' blades are moved to predetermined low pitch angle, for instance a positive 15 `In order to remove the mechanical low pitch stop to permit movement of the blade into the negative blade angle range, the valve 306 is moved upwardly whereupon the upper surface of the servo valve 394 is subjected to pressure fluid from the conduit 312 through ports 346 and 34d. When the Valve element 36d is moved downwardly against the urge of spring 35?, reduced pressure will be supplied from conduits 312 to conduit 352 which communicates with the low pitch stop release servo chamber 72. Movement of the valve element 306 upwardly also connects conduit to pressure.

Referring again to FIGURE 1A, the conduit 113, connected to the outlet side of the mechanically operated feathering pump 112, is connected with a spring biased check valve 356, such that under some conditions the output of the pump 112 can be connected to the high pressure conduit 146. Normally, however, the pump 112 is unloaded by unloading valve 353 having an inlet port 366 connected to the conduit 12S. The unloading valve 358 includes a plunger 362 which is mechanically actuated and in the position shown in FIGURE lA, the'l output of the pump 112 is by-passed to conduit 3641.

whichis connected with the drain conduit 120 as seen in sure potential in passage 366, and the lower of which is v subjected to the pressure potential in passage 380.l Passage 380 connects with a shuttle valve 382, opposite ends of which connect with passages 384 and 386. Passage 386 connects with the decrease pitch conduit 36 through conduit 290, and passage 384 connects with the increase pitch conduit 3S through conduit 384. Accordingly, the passage 364B and the lower surface of the land 378 will be subjected to the higher of the pressure potentials existent in the opposed chambers of the torque units so that the output pressure of pumps 128 and 130 will be regulated in accordance with the demands of the torque units. The spring 376 and the thrust of centrifugal force acting on the equal area valve 374 will always maintain the pressure potential in passage 366 at i approximately 450 p.s.i. above the higher of the pressure potentials in the torque units. 'Excess ow produced by the pumps 128 and 13G is diverted into the conduit 162. The relief valve 372 limits the maximum pressure of lthe pumps 12S and 130.

The conduit t4!) is connected to the branch conduit 172, and the branch conduit l72connects with a pressure reducer valve 366, of conventional design and construction, which operates to maintain a substantially constant low pressure of substantially 450 p.s.i. in conduit 312. Conduit 312 is connected to ports 39@ of the servo distributor valve 37) and to a supply port 392 and a speed sensitive valve assembly 394. The speed sensitive valve assembly includes a centrifugal responsive plunger 396 having a control land 39S, land a follow-up sleeve 466 having control ports 462. The control ports 402 connect with a passage 494, the passage 404 communicating with a servo chamber 466 of the distributor valve 376.

The plunger 396 is connected at 498 to a centrifugally responsive lever 416. The plunger 396 and the `lever 4 constitute a centrifugal mass, the center of gravity of which is indicated by numeral 412. Spring pressure is applied to the lever 410 at a point spaced to the left of the center of gravity 412 through a rod 414, the upper end of which constitutes a seat for a compression spring 416. The other end of the spring 416 engages an adjustable spring seat 4i3. In the position shown in FIG- URE 1A, the lever 41@ and the-plunger 396 are urged inta clockwise direction about a roller type fulcru`m 420 due to the thrust of centrifugal force in the direction of arrow 266, while the spring 416 opposes movement of the centrifugally responsive mass, under the thrust of centrifugal force. The fulcrum 420 is disposed within an elongated slot 422 of the lever 410, and can be moved to the lefthand side of the center of gravity denoted by numeral 412 to reverse the sense of the-centrifugally responsive mass as will be pointed out more particularly hereinafter.

The spring seat 418 threadedly receives a rod `424, the upper end of which is pivotally connected to an end of a bellcranlt 426. The intermediate pivot point of the bellcrank is carried by one end of a second bellcrank 42S. The other end of the bellcrank 426 is pivotally connected to a plunger 436. ln the position shown in FIGURE 1A, the plunger 436 abuts a threaded rod 432 having a cam follower 434 which engages a cam surface 436. The rod 432 threadedly engages a sleeve 438, and upon movement of the rod 432 due to the coaction between follower i0 43'4`and cam 436 the position of plunger 430 willpbe yacl-Vx justed so as to vary the load on the spring 416, and` hence the speed setting of the speed sensitive governor.

The rod 432 can be adjusted relative to the sleeve 438 Y before assembly of the propellers to adjust the speed setting of the governor in the reverse thrust range. VThe rod 424 can be adjusted relative to the spring seat 418 prior to assembly of the propeller to adjust the maximum speed setting of the governor inthe forward thrust governing range. The speed setting of the governor in the Iforward thrust range can also be varied by the pilot through movement of a cam 440 having a follower 442 with which a rod 444 has threaded engagement. The rod `444 is pivotally connected to the other end of the bellcrank 428. The intermediate pivot point of the bellcrank 428 is carried by an adjustable screw 446 which is utilized to vary the speed range of the governor in the positive thrust governing range. When the rod 444 is moved upwardly, as viewed in FIGURE 1A, the llefthand end Vof the -bellcrank 428 is moved downwardly, and

closed end of the sleeve 450 denoted by numeral 452 constitutes a piston surface subjected to the pressure lluid l in servo chamber 406. The upper annular surface 454 is subjected at all times to the constant reduced pressure in conduit 312. Since the area 452 is substantially greater than the area 454, the position of the` sleeve 456 can be controlled `by connecting the chamber 406 to pressure or drain. sleeve 456 is formed with drain ports 456 and 45d, as well as control ports 460 and 462. When the servo chamber 466 is connected to drain, as caused by upward movement l of the speed sensitive plunger 396, the sleeve 450 will t move downwardly due to pressure acting on the lannular surface 454, thereby connecting port 466 to drain port 456, and connecting port 462 to the pressure supply port 363. Under these conditions, high pressure uid `from conduit 366 will be supplied to the conduit 232which is connected to the increase pitch conduit 33 while the decrease pitch conduit 36 is connected to the conduit 2% which is connected to drain. Downward movement of t the sleeve 450 will pivot bellcrank 464 which is connected to the sleeve 49d so as to effect a 'follow-up upward movement of the sleeve 406. The sleeve 400 is normally biased upwardly by a spring 466 so that if the fluid pres-v sure system should fail, the sleeve 45t) will be moved downwardly. The arrangement of the yfollow-up sleeve 46 with respect to the plunger 396 results in movement of the distributor valve sleeve 45) in proportion to the amount of speed error.

A hydraulic jitter plunger 468 is connected to conduit 476, the conduit 470 communicating through ports 402 with the passage 464 and servo chamber 406. The jitter plunger 46S pulsates the oil in the chamber 406 so as to t reduce static friction. When the speed sensitive plunger 396 moves downwardly, the servo chamber 406 is condistance the decrease pitch port 460 is connected to the pressure supply passage 366 and the increase pitch port 462 is connected to drain. The bellcrank 464 will impart a follow-up movement to the sleeve 400 in a manner' f similar to that aforedescribed.

The valve guide for the. servo distributor valvel The propeller includes three nonrotatable, axially mov- Y movement of the lever 616. When the follower 614 is position of the propeller blades cannot be moved in the.

increase pitch direction above a negative 15 due to coaction between the follower roller 568 and the cam surface .S70 on the lever 410. This constitutes the hydraulic low pitch stop establishing the minimum negative blade angle during reverse governing. When the follower 614 is in the dwell 600, the minimum positive low pitch stop position of the blades in the forward governing range is established by the roller 572 and the cam surface 574 of the lever 410. The minimum hydraulic low pitch stop in the forward thrust governing range may be on the order of a positive 18, whereas the mechanical low pitch stop is slightly below this angle, for instance at a positive 15.

The follower 610 and the plunger 612 are utilized to adjust the speed setting of the pitch lock control valve 308 so as to maintain the speed setting of the pitch lock control valve substantially ve percent greater than the speed setting of the governor valve 394. Thus, when the foiiower 610 is in the inclined portion 606, the follower attached to the sleeve 442 is in the inclined portion 500 of the cam 440 whereby the speed adjustment of the governor spring 416 due to movement of the control ring 474 is accompanied by a like speedl adjustment of the spring 336 associated with the pitch lochl control valve. Similarly, when the speed setting of the governor spring 416 is a'maximum such as when the follower is in the dwell 502, the speed setting of the governor spring 336 will be a maximum and the follower 610 will be in the dwell 604. Conversely, when the speed setting of the spring 416 is a minimum wherein thefollower associated with the plunger 442 is in the dwell 498, the follower 610 is in-the the cam follower 628 during movement of the rod 508.

When the rod 8 is moved to the right, the lever 622 passages 234 and 238. Thus, the portion 632 of the slot 621 precludes vactuation of the shuttle valve 188 when the propeller blades are operated Vin either the beta 1 range or reverse thrust governing.

The rod 630 is Aconnected to a shoe 634 which follows the control ring 476. j The controlring 476 is moved byv rotation of high lead screws 636 having pinion gears 638 engaging ring gear 640. Ring gear l640 is connected to a lever 642. The lever 6 42 may be actuated by any suitable negative torque sensing mechanism for moving the control ring 476 to the left when the propeller is operated in the forward thrust governing range.

,The propeller control lever 584 is depicted in FIG- i URE 1A as beingin the forward thrust governing range, such that movement of the ring gear 582 in the clockwise direction will increase the speed setting of the governor to the full rated speed setting and further movement of the ring gear 582 in the-clockwise direction will call for emergency propeller feathering. Movement of the control ring- 582 in the counterclockwise directionj will reduce the speed setting of the governor to the mini-.

mum speed setting of 570 r.p.m. until the flight idle position is reached, after which continued counterclockwise rotation of the ring gear 582 will actuate the pitch stop control valve to remove the mechanical low pitch stop so as to enable the pilot to select any angle within the beta range between a negative 15 and a positive 18 if the speed of propeller rotation is below the speed setting of the governor.

the governor and esetablishing the minimum negative angle of the propeller blades in the reverse thrust range.

`the structural embodiment of the propeller will be described. The propeller hub 10 is formed with four radially extending sockets 12 spaced 90 apart. The hub 10 is formed with a rearwardly extending portion 11 and' a forwardly extending portion 13. A flanged annulus 15 is rigidly attached to the hub portion 13, and anannulus 17 is rigidly secured to the flanged annulus 15.

The feather reservoir housing 106 is rigidly attached to4 the annulus 1 7 s uch that the reservoir housing 166, the annulus 17 and the annulus 15 rotate with thehub 10.

The pump 108 is shown having a geared driving connection with an electricmotor 109.

:The hub 10 is supported for rotation about the fixed support shaft 78 Aby spaced radial bearings 19 and. 21 and a thrust bearing 23. A hollow drive shaft 25 is coaxially disposedwithin the stationary support shaft 78, the drive shaft 2S extending beyond the end of the support shaft 7S and having a radially extending flange portion 27. The ilange portion 27 is formed with a pair of spaced sets of straight spline teeth 29 and 31. The

spline teeth 31 are engaged by a ring nut 33 which 'threadedly engages the annulus 1S and retains the inner races of bearings 19` and 23 in fixed relation relative to the annulus 15 and the hub 10. The straight spline teeth 29 mesh with a setv of straight spline teeth 35 formed on the annulus 15, and the spiine teeth 29 and 35 constitute the driving connection between the shaft 25 andthehub 10. The annulus 15 and the drive shaft 25 vare maintained in xed relative axial positions by a snap ring 37.

A sealing ring 359. carried by the iianged end 27 of the f drive shaft 25 resiliently engages the support shaft '78 so as to prevent the loss of lubricant from the bearings 19 and 23. vThe inner race of the bearings 19 and 23 are held'inflxedrelationship to the support shaft 78 by a ring nut 41 which threadedly engages the support shaft 78. The inner .race of bearing 21 is maintained in xed relationship to the stationary support shaft 78 by a pair of sleeves 43 and 45a. The rearwardly extending portion 11 of'the'hu'b 10 supports a resilent sealing ring '47 which engages the ring 45 so as to prevent the loss of lubricant from the bearing 21. The outer race of the bearing 21 is retained in fixed relation to the portion 11 of the hub by a pair of sleeves 49 and 5l, tie sleeve A5i being engaged by a ring nut S3 which threadedly engages the portion 11 of the hub.

AV regulator reservoir is attached to the rear of the propeller hub and rotates therewith, the regulator reser- Voir including afront plate 55, a cover 57 and a stationary adapter assembly 59. The regulator cover Continued movement of theV ring gear 582 in the counterclockwise direction will operate the reverse governor thereby reversing the sense of l i Y has a plurality of removable access-V plates 6r suitably attachedA thereto and also car-ries a-slipV ring assembly 6st Suitable scaling rings `65 and 67 aredisposed be tween the rotating regulator parts and the stationary adapter assembly 59, and the front plate 55 andy the cover 57' are journalled for rotation about the stationary adapter assembly 59 by ball bearings 69 and 71, respectively. The regulator reservoir contains a quantity' of oilf which forms a torus during rotation of the propeller.. The nonrota'table control rings 472, 474 and 476 arev supported on the stationary adapter 59 for axial movement relative to the regulator assembly. In addition, a stationary pump power gear 73 is carried by the stationary adapter assembly 59 for actuating the pumps 128, 13G; and 132 during rotation of the propeller relative tothe stationary adapter assembly 59.

The hub 10, the feathering reservoir 166 and the regulator reservoir are enclosed by a spinnershelll 75 having a'centrally disposed air inlet opening 77 in the' nose portion thereof. Air entering the opening 77- flows across the outer periphery of the feathering reservoir 106 so` as to` cool the oil therein. This cooling' air flows through openings 79 in a spinner support bulkhead S1- which engages thc flanged annulus SI5V and escapesi toatmosphere through the cutout openings 83 in the=spinner shell 7-5 through which the blades 14 project'. The spinner shell 75 issuitably attached to the front p1ate55 of.' the regulator by fastening. means 77. of any suitable type. addition, the spinner shell 75 is formed with islands 76 which partially surround the cutout openings 83. The islands 76 are of airfoil shapeas seen in FIGURE 3- and form a' continuation of the airfoil portionof the-propeller` blade when the blades are ina predeterminedl blade angle position. v

With particular reference to FIGURE 4, the valve? assemblies and pumps of the propeller control system areV mounted on the front plate 55 of therv regulator.A The pumps 128, 130 and 132 are utilized to pumpfluid. fromthe reservoir and supply this fluid under pressure to the high pressure conduit 140 of the fluid pressure system, as hereinbeforer described. A fourth regulator pump:

denoted by numeral 87 also has its driveV gear` meshingV Awith the pump power gear 73 and; is utilized to supply lubricating uid to the bearings 19,21and23t The governor valve assembly 134 is mounted on the front plate 55 of. the regulator so that the centrifugally responsive elements thereof are located substantially radially with respect to the horizontal propeller axis. The hydromechanical feathering pump control valve 358 is. embodied in the. governor assembly 184. The-reverse governing actuator ISG is attachedr to the frontplate 55 adjacent. the governor valve assembly 184.. 'Ihe solenoid valvel assembly 18d is mounted` so that. the longitudinalr axis of the plunger is at right angles to a radiallline: intersecting the axis of propeller rotation soV a's' to eliminate the effects of centrifugal force on.v movement` of. theA solenoid. valve plunger.. The feathering control valve assembly 17S is radially mounted Within they regulator as isthe pitch lock and pitch stop controlvalve assembly 182. The jitter valve 468, the check valve 174,.. the feathering pump control valve 252V and the. auxiliary pump control valve assembly 142 are likewise attached` to` the regulator front plate 55.

With. particular reference to FIGURES 5 through 9, the structural embodiment of the: control mechanism` for.` the governor valve assembly and the reverse governor actuator will be described. The centrifugally responsive lever 41u is formed with an elongatedlongitudinal slotV 422 having av medial` portionv of greater widthA than the end portions. The fulcrum 424) structurally comprises a pair of rollers 421 and 423 which are disposed within the slot 422 and are supported by a slidable carriage 42511 having a bifurcated end' 427 which engages a pin 429. The pin 429 constitutes a part of a carriage 425, slidably supported in a rail assembly 577, and having an 1'6- elongatedt slot 433 therein constituting the equivalent ofthe slots 552 land 554Y in the levers 556 and S shown schematically in FIGURE lA. The levers 556 and 55S` are pivotally interconnected bythe pin 560 which constitutes apart ofa-carriage'561.

Carriage 561 constitutes the structuralequivalcnt of the rod 562 as shown in FIGURE 1A and is connected by means of a" pin 564 to the' intermediate portion of bellcrank' 566-. y

As seen in FIGURE 5', one end of the bellcrank 566 isA pivotally connected by means of a pin 567a to a carriage 569 which constitutes the structural equivalent of the nutv 102 as seen in FIGURE 1C. The other end of the bellcrank 566-is" pivotally connected by a pin 618 to a carriage' 619 which constitutes the structural equivalent of the pivoted lever 6162s seen in FIGURE 1B. The carria'ge 619 is also' pivotally connectedl to one endv of abellcrank 567 having an4 intermediate pivot 568 as see'n in FIGURE 6'. The other end-of the bellcrank 567 is' pivotally connected at 571` to a' lever 573. The lever 573 is pvotedv at 575v to the rail assembly 577 for the several carriages. The lever 573 has an elongated cam slot 579 engaged by al follower 581 attached to a' control shoe 90a which constitutes' the structural equivalent of the control shoes 493 and' 492 show-n in FIGURE 1A. The control shoe 490:1 is shown in the reverse governing posi-V tion in FIGURE 8 andl in the forward thrust governing position in FIGURE 6". The control shoe 490a is ate tached toa carriage 493 slidable in the railV assembly 577, and when the shoe 490a` and its follower 581v are moved so that the follower 581 isn in the extreme left-hand endof the slot 579, theV propeller will be' conditioned for emergency feathering operation;

As' seen in FIGURE 9; the carriagel 493"i'nclud'esT a roller 495 for positioning a lever 437 constituting the structural equivalent of the' camV plate 440 in FIGURE lA. Ac-

cordingly, during movement of the carriage 493fupwardly as seen in FIGURE 9, the lever 437 will pivot about its fulcrum 439 so as-to-/vary the load on the governor spring 416 and thus vary the speed setting of the governor. The' lever 573s and' hence the bellcrank 567 are only actuated when the cam follower 581 moves into the curved portions of the slot 579, and when feathering operation is selected or aparticular bladeA angle is selected in the beta' range,V or during a transition froml forward thrust governingto reverse thrust governing andvice versa.

A lever 58111 is supported by pivot pin 581b, lever Silla'l having a bifurcatedend 583'which receivesa pin-585 attached tothe valve plunger 518 of' thereverse governor' actuator 186. The plunger 518 hasla pin 519 disposedin the bifurcated end 521- of a lever' 523'. The lever 523 controls they mechanical latch depicted schematically by rod 532Y in FIGURE l-A associated with the rod 528 of. the actuator piston 522. structurally, the rod-1528y is pivotally connected by means of a'pin- 529 to one end ofY a` bellcrank 531 having a fixed intermediate-pivot point 5331 carried by theA housing' of the reverse governor actuator valve assembly 186; The other end of thebellcrank 53317 is pivotally connected by pin' 535-y to the carriage 431. The bellcrank 531 is shown inA the-forward thrust governing position in FIGURES. 5 andl 6 and in the reverse thrust governing position in FIGURE 8'. In the forward thrust.' governing` position, the roller 423 constitutes the fulcrum for the centrifugal responsive'flever 410 which is' located' to the'- right of the center of gravity of the centrifugally responsive lever and plunger assembly, whereas' when the lever 531 is' moved to thepostion of FIGURE 8, the carriage 425a`is` movedv upwardly as viewed' in FIGURE-7 so that roller 4211 constitutes' the'l fulcrum point for the lever 410 so that thefulcrumr point is disposed to the left of the center of gravityv of the centrifugally responsive leverand plunger assembly.

Operation When the propeller control lever 584 is in the-forward 17 thrust governing range, as indicated in FIGUREI 1A, the speed sensitive governor including the centrifugal plunger 396, the lever 410 and the spring 416 control the ow of uid under pressure to and from the pitch changing torque units. If the control lever 5,84 is moved in the counterclockwise direction within the forward governing range, the load on the spring 416 is reduced through cani 440 and the bellcrank 428 so as to reduce the speed setting of the governor. If the control lever 584 is moved in the clockwise direction as viewed in FIGURE 1A, the

speed setting of the governor is.4 increased. Normally,

the propeller control lever 584 is maintained in a position wherein the speed setting of the governor is at the full rated speed during flight of the aircraft so that during ight of the aircraft the governor will maintain propeller speed substantially constant at 1040 rpm. If propeller speed should exceed 1040 r.p.m., the speed sensitive plunger 396 will move upwardly so as to actuate the servo distributor valve 370 so as to direct fluid under pressure tocincrease the pitch position of the propeller blades. Conversely, if propeller speed should fall below 1040 r.p.m. the speed sensitive plunger 396 will move downwardly thereby actuating the servo distributor valve 370 so as to direct fluid under pressure to the pitch change torque units to reduce the propeller pitch.

During governing operation in the forward thrust range, the solenoid valve 180 is connected in a parallel ow path with the servo distributor valve 370, the solenoid valve lbeing energized by an electronic control system of the type `disclosed in the aforementioned copending application Serial No. 630,234. In addition, in a multiple power plant aircraft, the speed setting of governor can be adjusted through the synchronizing control lever 488. Moreover, during governing operation in the forward thrust range, the roller 572 coacts wit-h the cam surface 574 on the lever 410 to establish a minimum positive low pitch stop angle of the propeller blades in the forward thrust range. Thus, if the propeller should underspeed whereupon the governor will call for movement of the propeller blades in the decrease pitch direction towards a negative blade angle position, the feed-back gear `62 will act-nate the feed-back shaft 9'8, and the feedback shaft 98 will adjust the position of the roller 572 through the bellcrank 566 and the rod S62 so as to physically move the speed sensitive plunger 396 upwardly as viewed in FIGURE 1A when the propeller blades move below the angle of a positive 18. Actuation of the speed sensitive plunger 39-6 and the lever 410 by the roller 572 will in turn actuate the servo distributor valve 370 so las Ito interrupt the application of fluid under pressure to the decrease pitch chamber of the torque units. Thus, the minimum positive low pitch angle in the forward thrust governing range' is termed a hydraulic low pitch stop since the feed-back actuated roller S72 merely operates to mechanically position the speed sensitiveplunger 396 so as to increase the pitch position` of the propeller blades if the propeller blades move below a positive 18 when the propeller control lever 584is in the forward thrust governing range.

The propeller can be feathered at any time by energizing the solenoid 230, the energization being controlled lby -t-he pilot through a suitable switch, not shown. When the Solenoid 230 is energized, the valve plunger 226 is moved to the right, as viewed in FIGURE `1B thereby effecting a servo actuated shuttle valve 188 so as to 4rnove the shuttle valve 188 downwardly. When the shuttle valve 1818 is moved downwardly the increase pitch Conduit 3S is connected directly to .the high pressure conduit 140 while the decrease pitch conduit 36 is connected to drain through port `208, passage 242, conduit .364 and conduit 120. At -the same time, the shuttle valve 188 disconnects the high pressure conduit 140 from the conduit 223 which normally supplies high pressure fluid to the servo distributor valve 370; Thus, when the phuttle valve 1,88 is moved downwardly, Vthe :governor 18 valve assembly is disconnected from the torque units. When the solenoid valve 230 is energized, the electric motor 109 `for operating the feathering pump i108 is simultaneously energized to assume a suicient supply of liuid under pressure to move the propeller blades to the feathering range.

The shuttle valve18'8 can also be actuated to call for propeller feathering by movement of the selector valve 236 und-er the control of either rod 630 or rod 508. The rod 630 is operable to initiate propeller feathering at all times except when the propeller control lever 584 is in the beta or reverse governing ranges. When the rod 508 is moved to the left, as viewed in FIGURES 1A and 1B to call for propeller feathering, the feathering valve 358 is simultaneously actuated so as to connect the output of the pump 112 with the conduit 140 through the check valve 356. Moreover, when the control lever 584 is moved to the emergency feathering position, the speed sensitive plunger 396'is moved upwardly by the roller 572 through the rod 562 and the bellcrank 566 so as to actuate the servo distributor valve 370 to direct ow to the increase pitch chambers of the torque units. rl`his arrangement constitutes a safety feature since if the shuttle valve 188 should fail to operate for any reason, the governor valve assembly can direct lluid under pressure to the increase pitch chambers of the toque units. However, as aforementioned, if the shuttle valve 188 moves downwardly as viewed in FIGURE 1B due to downward movement of the selector valve 236, the high pressure supply to the servo distributor valve will be cut olf.

When a feathering operation is initiated, either manually or automatically, the toque units have their increase pitch chambers connected to the source of high pressure iuid and their decrease pitch chambers connected to drain. Accordingly, the propeller blades will be moved in the increase pitch direction, and when they arrive at a pitch angle in the feathering range, for instance, a positive the coacting lugs 90 and 92 are disengaged permitting the Belleville spring 94 to move the clutch member 84 into engagement with the ring gear 80. However, since the hydraulic pitch changing mechanism is capable of moving the propeller blades toward the 'full lfeathered position at a high pitch change rate, and since the hydraulic pitch changing mechanism can overpower the clutch member 84 to unfeather the propeller blades, as long as there is hydraulic pressure available for actuating the torque units, theclutch 84 will slip, or skid relative to the stationary ring gear 80. However, as soon as hydraulic actuation of t-he torque units terminates the clutch 84 will firmly engage the stationary gear 80, and will mechanically drive the propeller blades to the full feathered position upon propeller rotation in either direction.

When the propeller control lever 584 is moved into the beta range the valve 306 is actuated through rod 508 and lever S186 thereby releasing the mechanical low pitch stop and applying Iiiuid under pressure -to the servo chamber 594 to reset -t-he ygovernor spring 416 to the full rated rpm. of 1040. If the propeller speed is below 1040 rpm., the spring 416 will maintain the cam surface 574 of the lever 410 in engagement with the roller 572. Since the roller 572 is mechanically positioned through the cam 5110 and the bellcrank 566 in the beta range, the pilot can select any vangle between a positive 18 and a negative 15, and when the angle selected by the pilot has been reached by the propeller blades the feed-back mechanism will reposition the roller 572 through the bellcranlc 566 and the rod 562.

When the-propeller control lever 584 is moved to the reverse governing range, the governor sense is reversed since the fulcrum means 420 is moved to the position of FIGURE 2. i Concurrently, the roller 572 is moved out of operative engagement with the cam surface 574, andthe roller 568 moves into operative position with 

